We have observed a metallic solid (Al-14-at.%-Mn) with long-range orientational order, but with icosahedral point group symmetry, which is inconsistent with lattice translations. Its diffraction spots are as sharp as those of crystals but cannot be indexed to any Bravais lattice. The solid is metastable and forms from the melt by a first-order transition.

Metallic Phase with Long-Range Orientational Order and No Translational Symmetry

This review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data. The most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned. The Edwards-Anderson model of spin glasses and its treatment within the replica method and mean-field theory are outlined, and concepts such as "frustration," "broken replica symmetry," "broken ergodicity," etc., are discussed. The dynamic approach to describing the spin glass transition is emphasized. Monte Carlo simulations of spin glasses and the insight gained by them are described. Other topics discussed include site-disorder models, phenomenological theories for the frozen phase and its excitations, phase diagrams in which spin glass order and ferromagnetism or antiferromagnetism compete, the Ne\'el model of superparamagnetism and related approaches, and possible connections between spin glasses and other topics in the theory of disordered condensed-matter systems.

Spin glasses: Experimental facts, theoretical concepts, and open questions

A high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made. The gun consists of a nanotube film with a 1-millimeter-diameter grid about 20 micrometers above it. Field-emission current densities of about 0.1 milliampere per square centimeter were observed for applied voltages as low as 200 volts, and current densities greater than 100 milliamperes per square centimeter have been realized at 700 volts. The gun is air-stable, easy and inexpensive to fabricate, and functions stably and reliably for long times (short-term fluctuations are on the order of 10 percent). The entire gun is only about 0.2 millimeter thick and can be produced with virtually no restrictions on its area, from less than 1 square millimeter to hundreds of square centimeters, making it suitable for flat panel display applications.

http://science.sciencemag.org/content/sci/270/5239/1179.full.pdf

A Carbon Nanotube Field-Emission Electron Source

Bond-orientational order in molecular-dynamics simulations of supercooled liquids and in models of metallic glasses is studied. Quadratic and third-order invariants formed from bond spherical harmonics allow quantitative measures of cluster symmetries in these systems. A state with short-range translational order, but extended correlations in the orientations of particle clusters, starts to develop about 10% below the equilibrium melting temperature in a supercooled Lennard-Jones liquid. The order is predominantly icosahedral, although there is also a cubic component which we attribute to the periodic boundary conditions. Results are obtained for liquids cooled in an icosahedral pair potential as well. Only a modest amount of orientational order appears in a relaxed Finney dense-random-packing model. In contrast, we find essentially perfect icosahedral bond correlations in alternative "amorphon" cluster models of glass structure.

Bond-orientational order in liquids and glasses

PLUMED 2: New feathers for an old bird

It is well known that the properties of the electron gas have a strong influence on the structural and other physico-chemical properties of liquid and amorphous metals /1-3/. The possible importance of this for the stability of amorphous alloys has been pointed out by several authors /3-7/. The so-called Nagel-Tauc rule states that an amorphous alloy is most stable if the diameter of the Fermi sphere 2kp is equal to kp (first peak in the structure factor)

The Influence of the Average Electron Concentration on the Structure of an Amorphous Metal: A Computer Simulation*

RAI RADIO 1: “Area di servizio” -­ Intervista a Raffaella Conversano e Gaetano Manzulli www.rai.tv/.../ContentItem-­2d54f9c3-­fe29-­4e53-­99af-­ae8c7ce1eb22  RAI RADIO 1: “Area di servizio” -­ Intervista a Gaetano Manzulli www.rai.tv/.../ContentItem-­a13fe48c-­891d-­4dd8-­ae4a-­688db20f2b1  RAI RADIO 1: “Diversi da chi?” – Intervista a Raffaella Conversano www.radio.rai.it/radio1/diversidachi/view.cfm?Q_EV_ID=321903

Predizione contestuale di termini per fornire supporto a studenti con varie forme di disabilità

We discuss the problem of note taking versus having handouts provided by the teacher. We present a system we developed, composed by both hardware and software solution. The system requests students to be active in class taking notes, and yet helps them by relieving from the need of transcribing what is being presented. Moreover, it synchronizes the notes taken by students with a recording of the lecture in form of a video, so that student can use notes as anchors for reviewing portions of the lecture.

Let’s Reinvent Note Taking

We present our work about the development of a system, which allows taking notes during a lecture, and having the notes integrated in the video recording of the lecture itself. The notes become semantic markers into the video, and could possibly be shared with peers and teacher.

/pdf/work-in-progress-real-time-annotations-of-video-lectures-4apaoem3pa.pdf

Work in Progress: Real-Time Annotations of Video-Lectures

Semantic Web technology has been proposed as a key to enhance several aspects of elearning, such as annotation and adaptation to the students’ needs. Based on the same technology, we propose an approach to assist teachers in the process of selecting learning objects to build their own courses. We explicitly take into account teacher’s knowledge, experience and teaching style to maximize the likelihood of finding the best suited teaching material.

Marco Ronchetti

Papers

The Influence of the Average Electron Concentration on the Structure of an Amorphous Metal: A Computer Simulation*

Predizione contestuale di termini per fornire supporto a studenti con varie forme di disabilità

Let’s Reinvent Note Taking

Work in Progress: Real-Time Annotations of Video-Lectures

A semantic-web based framework for adaptive selection of learning objects during the authoring process.